Major Groups > Boletes > Boletus > Boletus spadiceus var. gracilis


Boletus spadiceus var. gracilis

[ Basidiomycetes > Boletales > Boletaceae > Boletus . . . ]

by Michael Kuo

Although this little bolete is currently classified as a diminutive "variety" of Boletus spadiceus, I will side with boletologist Ernst Both (1993), who believes it "probably deserves specific rank." Yes, it has a brownish cap that flashes green when a drop of ammonia is applied--and yes, its overall colors are similar to Boletus spadiceus. But its stature is completely different from that of the fairly stocky type variety and, more importantly, it is a mycorrhizal partner with hardwoods in eastern North America rather than associating with conifers in northern and montane areas.


Ecology: Mycorrhizal with hardwoods; growing alone, scattered, or gregariously; summer and fall; widely distributed from the Great Plains eastward.

Cap: 2-8 cm; convex, becoming broadly convex or almost flat; dry; finely velvety; yellowish brown to dull brown or reddish brown.

Pore Surface: Yellow, becoming olive yellow; sometimes bruising reddish brown; pores angular, especially near the stem, 1-2 mm wide; tubes to about 1.5 cm deep.

Stem: 3-6 cm long; up to 1 cm thick; more or less equal; solid; yellowish underneath fine reddish brown hairs and granules; not reticulate; basal mycelium yellow.

Flesh: Whitish in the cap; yellow in the stem; not staining on exposure, or staining faintly bluish.

Odor and Taste: Pleasant; not distinctive.

Chemical Reactions: Ammonia flashing green to blue-green on cap surface, then resolving to reddish brown; flashing greenish on flesh, then resolving to negative. KOH purple on cap surface; orangish on flesh. Iron salts olive on cap surface; olive on flesh.

Spore Print: Olive brown.

Microscopic Features: Spores 9-13 x 3.5-4.5 µ; smooth; subfusiform; yellow in KOH. Hymenial trama amyloid when first mounted. Hymenial cystidia fusoid-ventricose to fusoid; hyaline in KOH; to about 50 x 12 µ. Pileipellis a tangled layer of cylindric hyphae 9-12 µ wide, with rounded to subacute apices.

REFERENCES: Smith & Thiers, 1971. (Both, 1993; Bessette, Roody & Bessette, 2000.) Herb. Kuo 07080702, 07250801.

This site contains no information about the edibility or toxicity of mushrooms.


Boletus spadiceus

Boletus spadiceus

© MushroomExpert.Com

Cite this page as:

Kuo, M. (2007, December). Boletus spadiceus var. gracilis. Retrieved from the MushroomExpert.Com Web site: